P68
Spectrum: The vast majority of signals can decompose a number of different frequency sine waves, in some sine waves, the lowest frequency is called the fundamental wave of the signal, the rest is called signal harmonics, equivalent to the basic frequency of the signal. The sine wave component, which has a frequency equal to the base frequency integer, is called harmonics.
Comparison of image and spectrum after logarithmic transformation of 1.fft2 Fftshift
I=imread (' coins.png '); F=FFT2 (Im2double (I)); F1=fftshift (F); F=abs (F1); T=log (f+1); Imshow (F); I=imread (' coins.png '); F=FFT2 (Im2double (I)); F1=fftshift (F); F=abs (F1); T=log (f1+1); Figure;subplot (2,3,1); Imshow (f); subplot (2,3,4);p lot (ABS (f), ' R ') subplot (2,3,2); Imshow (F1); subplot ( 2,3,5);p Lot (ABS (F1), ' R ') subplot (2,3,3); imshow (t); subplot (2,3,6);p lot (ABS (t), ' R ')
2.
P68 logarithmic transformation about fft2 Fftshift spectrum